It is known to apply plaster, stucco and other textured wall finishes using hand held spray guns operated by compressed air. A typical spray gun used for this purpose is that sold by Bliss & Laughlin Industries under the trade mark GOLDBLATT. These spray guns are essentially adaptations of the compressed air operated spray guns utilized to spray paints and lacquers, modified so as to be able to handle sprayable materials of various textures and consistencies. Such guns are inevitably prone to occasional blockage, jamming and damage by the material being sprayed, and since it is often impracticable to dismantle the gun to correct such problems on site, an adequate supply of spare guns must be available. Moreover, such guns are neither designed for nor capable of spraying the coarse particulate materials used as a surface layer on some types of wall finish such as pebble-dash.
It is also known to provide fluid operated guns to project a stream of sand or grit for cleaning and removing previous finishes from walls by sand-blasting, but these are clearly not suited for applying particulate material to an unhardened wall finish, nor even if adapted for this purpose would they have the versatility to handle a wide range of particulate materials with a readily controllable rate of application. Moreover most such blasting guns require a fairly sophisticated system for delivering the particulate material.